Circuit arrangement for automatic telephone systems



Sept. 13, 1932. M M 1,877,678

CIRCUIT ARRANGEMENT FOR AUTOMATIC TELEPHONE SYSTEMS Filed Sept. 24, 1929 Ad P a l g e 5% InvenZ (By iiys.

Patented Sept. 13, 1932 UNITED STATES P E F C Z FREDBIK MARKMAN, OF STOGKI HIOLM, SWEDEN, ASSIGNOR TO TELEFONAKTIEBOLAGE L. M. ERICSSON, OF STOCKHOLM, SWEDEN, A CDMIE'ANY 01E SWEDEN I. 1

omourr ARRANGEMENT non AUTOMATIC 'rnnnriionn lsx sr Ms,

Application filed September 24, 1929, Serial No. 394,887, and in sweaen March 7.. 1 929.

Thepresent invention relates to automatic telephone systems and has for its object to.

improve the electric characteristics of the impulse circuit extending over the subscrib ers line over which circuits the impulses are sent from the impulse sender of the subscriber to set the selectors in the automatic exchange. It has been previously proposed to improve the impulse sending by connecting a shunt including a condenser to the impulse contact of the impulse sender. According to the present invention said shunt consists of a portion of the conducting bridge constituted by the call bell and its condenser,

which portion includes said condenser and is adapted to be short-circuited by the im pulse contact of the impulse sender over contacts on the hook switch of the telephone apparatus. In said shunt a part of the winding of the call bell is preferably included as an inductive resistance connected in series with the condenser.

The invention will be more closely described with reference to the accompanying branches.

l drawing in which Figures 1, 2 and 3 show three different embodiments according to the invention.

I n Figure 1, 1 and 2 designate the two branches of the subscribers lineextending from the subscribers set to the exchange. Normally a conducting bridge including the condenser 3 and the call bell winding 1 is interconnected between said two line shown diagrammatically. It is in known manner provided with contact springs 6, 7 which together constitutea normally closed impulse contact for the impulse sending and 1 two contact springs 8, 9, forming a normally The impulse sender is only over theimpulse contact 6, 7. 'The portion of said bridge notshort-circuited by the impulse contact is. at the same time shunted with the microphone and the telephone receiver over a contact 16 on the hook switch. Thelatter part of the bridge will then serve asa protection for the microphone 10 againsttransient voltages which otherwise would be generated by instantaneous current interruptions or renormal position the microphone 10 and the transformer of the telephone receiver as well as the part of the call bell winding 4. lying between the line branch 1 and the point are short-circuited over the contact 8, 9, whereby the said parts of the telephone apparatus are made inoperative during the'impulse sending. The connecting po nt 15 of the call bell winding-should be selected in j such a manner that the part of the call bell winding lying between the point 15 and the condenser 3 oifers an inductive resistance which is adapted to suit the electric characteristics of the'subscribers line. Said point may be-the middle point of the winding or any other point. p i

In the embodiment call bell winding consists of two parts 17, 18 which are normally connected I in series over a contact 19 on the hook switch.

In the bridgeincluding the condenser 3 and the windings 17, 18 also the winding 20 of an additional bell is included which, upon the telephone being lifted off, is short-circuited over a contact 21 onthe hook switch.

Otherwise the circuit arrangement is principally the same as that in F igure 1 with the difference onlythat the shunt including shown in Figure 'Q'the 1 the condenser 3 and the winding part 18 is normally open at the'contact 22 of the im'- pulse sender which contact, however, is closed as soon as the impulsesender is actuated to i send impulses said shunt being-then shortcircuited by the impulse contact 6, 7 in similar manner as in Figure 1.

Figure 3 shows a modification of the arrangement according to Figure 2. Normally the winding 20 of the additional bell and the into circuit over the commas, 26 and 27 on the hook switch the winding part 17 being then connected in shunt with the micro-' phone 10.. The, line-circuit is then closed over the contacts 25, 6, 7, the winding part 18 and through the microphone 10 and the part of the conducting bridge not short-circuited by the impulse contact is adapted to be short-circuited over contacts which are closed when the impulse sender is actuated to send impulses.

In testimony whereof I aflix my si nature.

. FREDRIK M RKMAN.

Winding part 17 connected in parallel. When I the impulse sender is actuated the condenser 3 and the winding part 18 are connected as in Figure 2 in shunt with the impulse contact 6, 7oVerthe contact 22. At the same time the microphone 10 and the winding part 17 are short-circu-ited over the contact 8, 9 and the telephone receiver over the contact 22.

I claim: l

1. In a substation telephone circuit two line conductors, a bell bridge with a condenser normally shunted to said conductors, a telephone book switch and an impulse sender,

the impulse contact of said impulse sender beingadapted to short-circuit a portion of said bellbridge including the condenser over contacts of the hook switch.

V 2. In a substation telephone circuit two line-conductors, a bell bridge with a condenser normally shunted to said conductors, a telephone hook switchand animpulse sender,

the; impulse contact of said impulsesender being adapted to short-circuit a portion of said bell bridge including thecondenser and a part of the call bell winding.

3. In a substation telephone circuit two line conductors, a bell bridge with a condenser normally shunted-to said conductors, a transmitter and a telephone receiver, a telephone hook switch and an impulse. sender, the impulse contact of said impulse sender being adapted, to short-circuit a portion including the condenser of said bell bridge over contacts of the hook switch, while the part of the conducting bridge not 'short-circuited by the impulse contact being adaptedto be Connected in shunt with the transmitter and the receiver over contacts of the hook switch. 4. Ina substation telephone circuit two line conductors, a bell bridge with a con- .denser normallyshunted to'said conductors, a transmitter and a telephone receiver, a telephone hook switch and an impulse sender,

the'impulse contact of said impulse sender f being adapted to short-circuit a portion including the condenser of said bell bridge over: contacts of thehook-switch, while the 

